1. Field of the Invention
This invention relates to systems for removably sealing a closure member to an opening, such as a window shade to a frame using magnetic attractive forces.
2. Description of the Prior Art
It has long been appreciated that magnetic forces could be desirably utilized to secure various types of coverings to a window frame. For example, U.S. Pat. No. 3,679,505 (Hinderaker and Nelson) discloses a method of sandwiching a flexible insect screen between parallel strips of a flexible rubber based magnet such as Plastiform.RTM., manufactured by Minnesota Mining and Manufacturing Company, St. Paul, Minn., such that when the screen is magnetically attracted to a vehicle window frame substantially no gaps between the screen and frame are present, thus facilitating the use of the vehicle for sleeping accommodations during camping trips.
Flexible window coverings are also disclosed in U.S. Pat. Nos. 2,321,078 and 2,514,316. While not there suggested, such coverings could also be held in place via magnets disposed about the periphery of the covering. U.S. Pat. No. 3,133,324 discloses the use of magnetic fasteners when using conventional rigid window constructions.
All known window systems using magnetic attraction provide a magnet construction on the closure element and a magnetizable element providing a magnetic flux return path in the frame. In some systems, the flux path is present as a result of the intrinsic ferromagnetic nature of the frames such as a vehicle body, while in other systems a separate ferromagnetic strip is inserted into the frame. Even when "flexible" rubber based magnets such as employed in U.S. Pat. No. 3,679,505 are so used, a relatively thick and stiff member is present which precludes using the closure member in roll-up form ala a conventional window shade.